Mass spectroscopy is a uniquely valuable tool in chemical analysis used in support of synthesis of compounds of biological importance, because of the very high sensitivity of the method and its ability, when coupled with separation techniques such as gas or liquid chromatography, to characterize mixtures of compounds. This proposal requests funds to acquire a new quadrupole mass spectrometer/gas chromatograph system and to upgrade an existing quadrupole mass spectrometer. Both the upgraded and the new instrument would primarily support the research efforts of NIH-supported investigators in the Yale Chemistry Department, whose projects range from synthesis of natural products and other compounds of biological interest to elucidation of reaction mechanisms and determination of energies and conformations of organic molecules. A common need in these various projects is for routine access to a mass spectrometer of modest performance, capable of nominal mass measurement to ca 1000 daltons, to characterize the products of the synthetic efforts central to these projects.